Currently, a conductive adhesive (or bonding agent) is used to mount a crystal blank of a crystal oscillator on a ceramic package of the crystal oscillator. A dispenser is used to coat the conductive adhesive on a base within the ceramic package.
FIGS. 1A and 1B are diagrams illustrating an example of a structure of an oscillator in related art.
As illustrated in a side view in FIG. 1A, an oscillator 100 includes a ceramic package 112, a crystal blank 114, and a circuit 116. The circuit 116 includes an oscillator circuit, a control circuit, an output buffer circuit, and the like. The crystal blank 114 and the circuit 116 are provided within the ceramic package 112.
As illustrated in a top view of FIG. 1B, a pair of excitation electrodes 118 is arranged to sandwich the crystal blank 114. A connection line 120 extends from each of the excitation electrodes 118 to a corresponding end part of the crystal blank 114 to connects to an electrode pad 122 provided on a base 112a of the ceramic package 112. The electrode pads 122 connect to the circuit 116 via a connection line (not illustrated). The electrode 118 on the crystal blank 114 is bonded to the base 112a by a conductive adhesive 124 in order to electrically connect to the corresponding electrode pad 122.
FIGS. 2A and 2B are diagrams illustrating another example of a structure of an oscillator in related art. In FIGS. 2A and 2B, those parts that are the same as those corresponding parts in FIGS. 1A and 1B are designated by the same reference numerals, and a description thereof will be omitted.
As illustrated in a side view of FIG. 2A, the ceramic package 112 has bases 112a and 112b. 
As illustrated in a top view of FIG. 2B, a pair of connection lines 120 extend from the pair of excitation electrodes 118, in mutually opposite directions, to diagonally opposite end parts of the crystal blank 114 to connect to the pair of electrode pads 122 provided on the respective bases 112a and 112b of the ceramic package 112. The electrodes 118 on the crystal blank 114 are bonded to the respective bases 112a and 112b by the conductive adhesive 124 in order to electrically connect to the corresponding electrode pads 122.
FIGS. 3A through 3D are diagrams for explaining an example of an adhesive coating process for the oscillator illustrated in FIGS. 1A and 1B.
As illustrated in perspective views of FIGS. 3A, 3B and 3C, when coating the adhesive 124 on the base 112a, the dispenser 126 is lowered to a position where the electrode pad 122 is provided, the adhesive 124 is supplied from the dispenser 126 onto the base 112a, and the dispenser 126 is raised from the lowered position. But as illustrated in a top view of FIG. 3D, when a coating position of the adhesive 124 is slightly shifted or, a coating region of the adhesive 124 spreads, the coated adhesive 124 may project outside the electrode pad 122 to cause a slight difference in the bonding state of the crystal blank 114 depending on the positional shift or regional spread of the adhesive 124. Such a slight difference in the bonding state of the crystal blank 114 may cause an oscillation frequency of the oscillator 100 to become unstable with time or, may stop oscillation. Such a problem of the oscillator 100 illustrated in FIGS. 1A and 1B may occur in a similar manner in the case of the oscillator 100 illustrated in FIGS. 2A and 2B.
A known pattern forming method may be used to coat the adhesive. For example, the pattern forming method forms a pattern by filling a print material into an opening penetrating a printing plate, and printing the print material onto a target object. The printing plate may be removed from the target object after curing or semi-curing of the print material.
An example of a screen printing method is proposed in a Japanese Laid-Open Patent Publication No. 2000-233560.
Because the printing plate is removed from the target object after curing or semi-curing of the print material, the print material is unlikely to flow and cause a positional error of the pattern that is formed. However, when the pattern forming process is used to coat the adhesive, it may not be possible to bond the crystal blank 114 to the base 112a or to the bases 112a and 112b in a manner such that the oscillation frequency of the oscillator 100 is unaffected by the bonding.